Axon collateral ( Cajal, 1899 ) : A branch of an axon trunk that is typically thinner than the trunk and arises at a roughly right angle. First pointed out by Deiters (1865, Tab. 1, Fig. 1-b; see Van der Loos, 1967, p. 44), Golgi (1873) established their existence with his black reaction and noted their roughly right angle of origin (he called them branches or side fibrils); apparently named by Cajal (1899, p. 329, "collaterals of axons"). A short form is collateral (Waldeyer, 1891).

Dendritic spine ( Cajal, 1899 ) : A short thin extension from a dendrite (His, 1889) that typically comes off at roughly a right angle. The extension may or may not have a swelling on the end; when it does, the swelling (spine head) is typically postsynaptic. They were discovered and named spines by Cajal (1888, p. 4, "espinas" in Spanish) and named dendritic spines by Cajal (1899-1904, vol. 1, Fig 14); also see Peters et al. (1991, p. 92), Alvarez & Sabatini (2007).

Nerve terminal ( Cajal, 1899 ) : Synonym for axon terminal (Barker, 1899); term used for Golgi material by Cajal (1899, p. 67).

Terminal ( Cajal, 1899 ) : A general term that refers to an axon terminal (Barker, 1899) and/or synapse-of-passage; its characteristic feature is a slight rounded swelling that is presynaptic; Cajal used for Golgi material, p. 67.